!752

!include #1004863 // Dynamic Concepts

sclass CKnownString extends Concept {

  S s;

  *() {}

  *(S *s) {}

}

sclass CUnknownString extends Concept {}

sclass CUnknownCharacter extends Concept {}

sclass CKnownCharacter extends Concept {

  char c;

  *() {}

  *(char *c) {}

}

sclass CharInString extends Concept {

  new Ref string;

  int index;

  *() {}

  *(Concept string, int *index) { this.string.set(string); }

}

sclass CUnknownInt extends Concept {}

sclass CKnownInt extends Concept {

  BigInteger value;

  *() {}

  *(int value) { this.value = bigint(value); }

}

sclass CKnownEquals extends Concept {

  new RefL what;

}

sclass Question extends Concept {}

sclass WhichCharacterIsIt extends Question {

  new Ref character;

  new Ref answer;

  *() {}

  *(Concept character) { this.character.set(character); }

}

p {

  CKnownString s = new CKnownString("hello world");

  CharInString c = new CharInString(s, 3);

  WhichCharacterIsIt question = new WhichCharacterIsIt(c);

  tryToAnswer(question);

}

svoid tryToAnswer(WhichCharacterIsIt question) {

  // We need a rewriting engine here

}